In between various customer projects, I have slowly been making progress on my engine. The Heads are twin cam 88 originally, but have been modified. I reshaped the majority of the fins, rounding them around many of the sharp edges. Here is an overall view of the cylinder, head, and rocker box mocked up.

A typical twin cam has aluminum cylinders with an iron sleeve pressed into it. I had Randy at Hyperformance make me billet iron cylinders. The advantage being that there is no way for the iron sleeve to become loose in the aluminum cylinder, because it is all iron! These are secured by a “head and base” stud setup, much like a knuckle, pan, or shovelhead would have been. Here a set of 4 studs hold the cylinder to the crankcase, and another set of 4 hold the head to the cylinder.

An evo or twin cam, traditionally, used a set of 4 studs that ran all the way through the head, cylinder, and into the case. This is a simpler way to attach all the parts, but not as strong.

In addition to the stud conversion, I have adapted the heads to use a superior head gasket method, the metal o-ring. On a stock twin cam (or any other harley) a composite flat gasket was used, sandwiched between the head and cylinder. They work fine, but can blow out if extreme cylinder pressures are achieved. The metal o-ring setup eliminates the flat gasket, instead using a series of steps machined into both the head and cylinder, with a copper ring integrated into it. All of the mating surfaces make contact with each other at the exact same time. This requires extremely precise machining, but results in a nearly indestructible union. I can only assume, too, that heat transfer between the head and cylinder will be improved, due to the metal to metal contact.

Here is the top of the cylinder. The surface rust inside the bore will be gone when the final honing happens.

You may have noticed that there are no oil drain passages in the cylinder. This is because I have re-routed them to the outside of the head and cylinder. This is good for 2 reasons. One is it keeps the oil cooler, since it is not touching the approx 300 degree cylinder walls. The second is that there is no chance of oil weeping between the head and cylinder surfaces, since it bypasses that area completely.

I had to machine a passage through the fins of each cylinder, through the wall, and into the oil drain passage inside the head. This was then tapped for a custom made fitting. Obviously, the original hole underneath has to be plugged as well.

Here is the stainless drain fitting coming out of the head. It has a 6 AN fitting on the end for hose attachment…

I have also added compression releases to the heads. Compression releases are simply tiny valves that allow the cylinder pressure to be bled off as the starter motor rotates the engine. This takes a huge strain off the starter motor and battery, and they simply pop shut when the first combustion occurs, allowing the engine to start. It is unusual to see them on motors with small displacement, but there is no downside to using them. Also, my compression ratio and the resulting cylinder pressures are far higher than either a stock evo or twin cam, so despite the small displacement, the starter will still need all the help it can get.

Installing compression releases is easy with the right tools. It requires a precise hole to be drilled and tapped, which enters the combustion chamber between the exhaust valve and the spark plug hole. More to come…

After a brief hiatus I am back on the “mini stroker” chopper project. I decided that it was the right time to make handlebars. The first step, for me anyway, is to make a wire form of what I want so I can hold it up to the bike and get a visual. This is not a precise thing, rather just a basic reference. I know roughly how much rise I want, and know roughly the whith, but that still leaves a lot of room for creativity.

I am making these bars out of 304 stainless steel, 7/8″ OD, .120″ wall thickness, seamless tubing. I will end up using about 4 feet of it, approx $80 worth of raw materials. This is opposed to the catalog bought, .049″ wall, recycled mild steel, chromed Chinese bars found on most “custom bikes”.

I start with the center bends and work outward. I have reference marks drawn on the tubing. This is so I can take the bars out of the bender, check them, then put them back in the exact same location for further bending. Speaking of bending, this is my bender. It consists of a typical bottle jack and various mandrels, a few of which I made specifically for tight radius handlebar bends.

For tight radius bends like these, I use two different mandrels, a gradual “starter” mandrel and a secondary tighter one.

The hardest part of making bars is keeping everything symmetrical. The exact location of the bends, the angles relative to each other, equal pullback on each side, etc. This is all done through bubble levels, angle finders, and measuring them against a flat table. There are a minimum of 6 mandrel changes, each of which entails some dis-assembly of the bender. Oh yeah, the material is springy, so I have to “overbend” each bend past the point I want, then let it spring back slightly to where I want it.

Almost done with the bending stage….

The next stage is polishing them. Sounds easy enough but keep in mind I cant just go straight to the buffer- First I have to sand them. The buffer can only take out microscopic scratches, not the deeper ones left from the manufacturer. For that I need my trust Burr King sander, set up with a slack belt, and a variety of sanding grits.

Not a great pic I know, but trying to simultaneously sand the bars and take a picture was not easy. Same for the buffing. Needless to say there were about 2 hours worth of sanding and buffing to get them to a mirror finish level.

I threw the grips on there to see how it looked. I am happy for now, but there is always the chance that they will need further modification as the bike evolves.

I’m sure I will get many comments on my “sweet chrome apes” from the local do-rag crowd. Followed by “how much for a set uh dem?”. Followed by a look of disgust and confusion…